Doing a web search for "Early American gunsmiths" will generate a lot of information. The links below are just such examples. German and Swiss gunsmiths came to Pennsylvania during the colonial period. A bit of research may answer your questions about where they came from. Take care...
Joe
http://www.metmuseum.org/publication...f.bannered.pdf
http://www.claytoncramer.com/popular...lyAmerica.html